U.S. Pat. No. 4,036,486, incorporated herein by reference, describes a mat board cutter by which a mat board is cut to have a desired peripheral size to fit within a desired frame and to have a desired central opening through which a picture being framed is visible.
As described in greater detail in U.S. Pat. No. 4,036,486 cutting the mat board requires sliding a cutter-carrying body along a guide rail with a knife on a cutter device pivotably carried on the body in engagement with the mat, which mat is held in a predetermined position by abutment means on a base and a clamp bar on which the guide rail is mounted. Sliding engagement between the body and guide rail is afforded by boring the body to provide a cylindrical bearing surface defining a through opening receiving a peripheral guide surface on the rail. The body is bored to initially provide close-fitting engagement between the bearing and guide surfaces. With use, however, wear on one of the surfaces (normally the bearing surface on the body which is made of a softer material, such as brass, then the guide rail which is typically made of steel) can allow the body to move out of its intended path so that cuts made by the knife are not as straight as may be desired.
Such wear has been compensated for on prior art cutter-carrying bodies by attaching plates on the ends of the body with screws, with arcuate edges of the plates bearing against sides of the guide surface. Such plates, however, are both, expensive and difficult to adjust.